The present invention relates to a rotary pump and, more particularly, to a rotary pump having an eccentric rotor adapted to make an eccentric motion relatively to the axis of the pump shaft, so as to cause a pumping action in a pump chamber formed in a pump casing.
Generally, in the rotary pump in which the pumping action is performed by an eccentric rotation of an eccentric rotor accommodated in a pump casing, the eccentric rotor is rotated by the torque transmitted from the pump shaft, while being pressed in the direction of the eccentricity so as to make a sliding contact with the inner peripheral surface of the pump chamber. In order to achieve a high pump efficiency, it is desirable that the eccentric rotor makes the eccentric rotation keeping a sliding contact with the inner peripheral surface of the pump casing, while being pressed strongly in the direction of the eccentricity. At the same time, it is desirable that the pump casing is completely sealed to avoid the external leak of the pumped fluid.